cumulativetodelta: initial data points are included for monotonic counters

[lincolnmantracer]

Component(s)

processor/cumulativetodelta

What happened?

The cumulative-to-delta processor includes the initial delta from zero to the current value as a data point:

opentelemetry-collector-contrib/processor/cumulativetodeltaprocessor/internal/tracking/tracker.go

Lines 92 to 104 in 34b31da

	if !ok {
	if metricID.MetricIsMonotonic {
	out = DeltaValue{
	StartTimestamp: metricPoint.ObservedTimestamp,
	FloatValue: metricPoint.FloatValue,
	IntValue: metricPoint.IntValue,
	HistogramValue: metricPoint.HistogramValue,
	}
	valid = true
	}
	return
	}
	valid = true

Even for monotonic counters, this is counterintuitive and noisy. For example, here is what that looks like in real production data when the collector is restarted:

The processor should drop the first data point regardless of whether the dataset is monotonic or not, because the first data point can not be guaranteed to be a delta.

Collector version

0.70.0

Environment information

Environment

OS: Ubuntu 22.04

OpenTelemetry Collector configuration

<snip>
processors:
  cumulativetodelta:
    include:
      metrics:
        - "bytes_total\\z"
      match_type: regexp
  metricstransform:
    transforms:
      - include: "(.*)_bytes_total\\z"
        action: insert
        new_name: "$${1}_bitrate"
        match_type: regexp
        operations:
          - action: experimental_scale_value
            # The starting unit is bytes per 5s. 0.2 * 8 = 1.6
            experimental_scale: 1.6

Log output

No response

Additional context

No response

[github-actions]

Pinging code owners:

• processor/cumulativetodelta: @TylerHelmuth

See Adding Labels via Comments if you do not have permissions to add labels yourself.

[github-actions]

This issue has been inactive for 60 days. It will be closed in 60 days if there is no activity. To ping code owners by adding a component label, see Adding Labels via Comments, or if you are unsure of which component this issue relates to, please ping @open-telemetry/collector-contrib-triagers. If this issue is still relevant, please ping the code owners or leave a comment explaining why it is still relevant. Otherwise, please close it.

Pinging code owners:

• processor/cumulativetodelta: @TylerHelmuth

See Adding Labels via Comments if you do not have permissions to add labels yourself.

[TylerHelmuth]

Closed via #18224